Update README.md

Author: malczuuu

README.md

@@ -38,21 +38,15 @@ It is intended to be used as a **foundation** for other libraries or application
 import io.github.malczuuu.problem4j.core.Problem;
 import io.github.malczuuu.problem4j.core.ProblemException;
 
-public class ExampleClass {
-
-  public void method() {
-    Problem problem =
-        Problem.builder()
-            .type("https://example.com/errors/invalid-request")
-            .title("Invalid Request")
-            .status(400)
-            .detail("not a valid json")
-            .instance("https://example.com/instances/1234")
-            .build();
-
-    throw new ProblemException(problem);
-  }
-}
+Problem problem =
+    Problem.builder()
+        .type("https://example.com/errors/invalid-request")
+        .title("Invalid Request")
+        .status(400)
+        .detail("not a valid json")
+        .instance("https://example.com/instances/1234")
+        .build();
+throw new ProblemException(problem);
 ```
 
 ## Usage